Satellite communication is rapidly growing today as an alternative to communication via terrestrial communication systems. The rapid growth of the Internet network as well as requirements for a variety of broadcast television channels led to development of applications of data broadcasting and digital video broadcasting via satellite. However, development of various issues related to satellite communication, such as ensuring a reliable quality of service for different users of on-demand unicast broadcasting services, is still required. It is appreciated that the problems of satellite communication are not limited to communication via satellite only, and that satellite communication is used throughout the present specification and claims by way of example only.
Continued efforts to standardize data broadcasting and digital video broadcasting has resulted in current standards that are found in the following publications:
a publication entitled “ATSC Data Broadcast Specification—DRAFT ATSC Standard” revised Jan. 11, 1999;
a publication entitled “Implementation Guidelines for Databroadcasting”, SI-DAT 382 Rev. 3, dated Jun. 18, 1997; and
a publication entitled “Digital Video Broadcasting (DVB); DVB specification for data broadcasting”, TS 101 192 V1.1.1 (1997-10) Technical Specification by the European Telecommunications Standards Institute (ETSI).
An aspect of the efforts to ensure a reliable quality of service to users is mentioned in unpublished Israel patent application 129,230 which describes a system for determining that all of a scrambled message has been successfully received.
An access control system for broadcasting services is described in an English translation of a publication entitled “Access control system for the MAC/packet family: Eurocrpyt”, dated March 1989. Additional access control systems for broadcasting services are described in U.S. Pat. Nos. 5,282,249 and 5,481,609 to Cohen et al.
Quality of service in packet networks is described in an article entitled “Teaching IP new tricks: VLANs, QoS, And Other Advanced LAN Protocols”, by Lee Goldberg, in Electronic Design magazine, dated Sep. 1, 1998.
The disclosures of all references mentioned above and throughout the present specification are hereby incorporated herein by reference.